Field of the Invention
Embodiments of the invention relate generally to a device for assisting with the handling of an instrument or tool by means of a jointed mechanical structure. One particular embodiment of the invention relates to imaging, more particularly, imaging within the scope of a breast echographic examination of abnormalities detected in breast tomosynthesis.
Description of Related Art
Tomosynthesis is an x-ray imaging method with which it is possible to obtain a three-dimensional representation (3D) of an object of interest in the form of a series of successive cuts. These cuts are reconstructed from projections of the object of interest under various angulations.
To do this, the object of interest is generally placed between a source emitting X-rays and a detector of X-rays. The source and/or the detector are mobile, so that the direction of projection of the object on the detector may vary (typically over an angular range of 30°). Several projections of the object of interest are thereby obtained under different angulations, from which it is possible to reconstruct a three-dimensional representation of the object of interest, generally by a back-projection method well-known to the person skilled in the art.
Tomosynthesis is particularly used in screening and diagnosing breast cancer. In this case, this is referred as breast tomosynthesis or 3D mammography. FIG. 1 schematically illustrates an imaging device 1 for acquiring two-dimensional (2D) projection images of an organ B and for reconstructing a 3D image of this organ by tomosynthesis.
X-rays from a source 4 are emitted according to different angulations towards the organ B. After having crossed the organ B, they are detected by a detector 3 forming a set of projection images.
A three-dimensional representation of the organ B, typically in tomographic cuts (images) parallel to the detector 3 is reconstructed by a tomographic reconstruction method well-known to the person skilled in the art.
As in conventional 3D mammography, the breast of the patient is in particular compressed between the detector 3 and a compression paddle 2 during the tomosynthesis examination. The practitioner will analyze tomographic cuts in order to detect a possible lesion. It may happen that the practitioner wishes to conduct an additional examination for example by means of an echographic probe over an area which he/she will have identified. Customarily, the mammary echography examination is carried out with the patient lying on her back or slightly turned to the side. The breast is not compressed.
In order to localize the lesions to be evaluated with the echographic probe, the radiologist has to mentally “superpose” the 3D tomosynthesis image over the breast of the patient. This superposition is very difficult, since the patient is standing (or sitting) with the breast compressed in tomosynthesis and lying on her back with the breast which is not compressed in echography.
A solution to this problem is to carry out the echographic examination straightaway after the tomosynthesis examination, with the patient in the same position. The breast of the patient is compressed before the tomosynthesis examination and decompressed once the echographic examination is finished. The tomosynthesis system should be equipped with a compression paddle compatible with echographic examination (the paddle should be “transparent” to sound waves emitted by the echographic probe).
In that case, the images acquired by the echographic probe and the tomographic cuts correspond to a same position of the breast of the patient.
However, in order to bring the probe to the level of the possible lesion, the practitioner has to use tomographic images as a reference for localizing the lesion.
This is not without difficulty since the practitioner has to mentally reconstruct the localization in the space of the possible lesion from tomographic images.
Devices which provide assistance to a user during the handling of an instrument or tool are already known in robotics. To do this, the assistance device gives the possibility of imposing a kinematic constraint to the instrument or tool in order to position it so that the user may carry out a task. It is specified that by task is meant a defined action according to a certain number of degrees of freedom which the user wishes to exert with the instrument or tool.
These devices today are complex, bulky and expensive given that they require many motor drives. Moreover assistance devices are known for which the jointed mechanical structure is actuated according to a number of degrees of freedom of less than that which the structure provides to the instrument or tool.
For example, in surgery, jointed arms are already known which will preposition the end of the arm on which the tool is jointed. Once the arm is thereby pre-positioned, the user may cause his/her tool to perform a particular movement of translation or rotation while the arm remains constrained in this position.
Such jointed arms however do not provide guidance of the user in the movement which he/she gives to the instrument or tool. In the particular case mentioned above, these known devices would not provide guidance in the positioning of the echographic probe. Indeed, the number of motor drives is not only less than the number of degrees of freedom of the tool but also less than the number of degrees of freedom required for accomplishing the task.
Therefore, there exists a need for a device for assisting with the handling of a tool or of an instrument by means of a jointed mechanical structure which is simple, inexpensive with a reduced number of motor drives but which allows actual guidance of the movement of the tool or of the instrument.